It is well known that organic oxygenates, particularly methanol and dimethyl ether, can be converted to a wide range of hydrocarbons, including aromatics, olefins and paraffins, over a special class of crystalline aluminosilicate zeolite catalysts of which H-ZSM-5 is the most preferred. The process is generally referred to as the MTG process at least partly because the hydrocarbon product has a high octane value and is useful as a gasoline blending stock. The MTG process is described in many patents and publications, including U.S. Pat. Nos. 3,931,349; 3,969,426; 3,899,544; 3,894,104; 3,904,916; and 3,894,102; the disclosures of each of which are incorporated by reference.
U.S. Pat. No. 4,304,951 describes a process for hydrotreating a 200-400° F.+ bottoms fractions resulting from conversion of methanol to gasoline in order to decrease the durene content of the bottoms fraction and produce distillate.
There is, however, continuing interest in developing new applications for the hydrocarbon product of the MTG process, particularly at sites which have a plentiful supply of natural gas which can be converted to the methanol and dimethyl ether feedstocks of the MTG process. In addition, there is growing interest in developing processes which allow greater flexibility in the final product slate of the MTG process according to site needs and customer demand.